More and more portable equipment use sophisticated features such as color display, stereo audio and connectivity solutions. Some examples include: GPRS, Wireless LAN and Bluetooth along with video and camera functionality. However, consumers do not want large, bulky equipment. Instead, they demand tiny form factors and light-weight, user-friendly designs with long battery life. This consumer preference poses a dilemma for electrical design engineers. More power needs to be delivered to the system, and there is less space and battery capacity available to design the power supply for today's sophisticated portable devices. These technical requirements translate into the need for integrated circuits that offer fast and accurate battery charging, higher-power conversion efficiency, lower-power consumption, and greater functional integration while occupying less space.
Previously, a few linear regulators were sufficient to design a simple power supply. However, running a system on the lowest possible energy budget and dissipating the least amount of heat in space-constraint designs forces the use of more complex, but significantly more power-efficient, switch-mode DC/DC converters. They contribute to longer battery life and minimize board space.
New low-profile packaging technology, low-power process technology and advanced power management methodologies simplify design complexity. Compared to previous leaded packages, one cutting-edge packaging technology established in the market recently is the QFN (Quad Flat No-Lead) package.
While conventional QFN packages are acceptable, a number of improvements can be made to QFN type packages. For example, improvements could be made to locking the molding material in the package to the leadframe structure of the package, preventing moisture from passing to the die in the package, and preventing solder between a die and die attach pad from overflowing off of a die attach pad and keeping it confined to the die attach pad.
Embodiments of the invention address these and other problems individually and collectively.